ECR Posted February 24, 2021 Share Posted February 24, 2021 Out of boredom I just watched a you tube video on changing the timing belts on a Ferrari 355. When it came to tensioning the auxiliary belts (alternator, ac etc) there is a special tool that Ferrari use to measure the tension. The tool was expensive and so when the job was complete and the belts tensioned correctly, he used a free app from Gates which measures frequency on specialised bike drives to record the frequency of a correctly tensioned Ferrari belt. This can then be used by any Ferrari owner rather than them having to buy the special tool. It’s simple to use, you just twang the belt like a guitar string and the App shows the frequency. I see no reason why this can’t be used on any engine with manual belt tensioning provided the correct frequency has been published by a kind user. Useful if you don’t have a belt tension measuring tool perhaps. When I am next to my spare engine, I’ll do some back to back comparisons on my VX timing belt and publish the frequency target if it works.. Link to comment Share on other sites More sharing options...
Wrightpayne Posted February 24, 2021 Share Posted February 24, 2021 If the belt stretches a bit will it need a tune up :-)Interesting stuff - Thanks for sharing. Link to comment Share on other sites More sharing options...
Roy Blyth Posted February 25, 2021 Share Posted February 25, 2021 You mean something like this...? https://www.pandamed.co.uk/product/tuning-fork-with-base/ Link to comment Share on other sites More sharing options...
revilla Posted February 25, 2021 Share Posted February 25, 2021 I just can't see how that would work with something like a K Series. When tensioning the belt, you turn the engine clockwise (normal running direction). All of the tension is on the drive side, the straight belt run down from the exhaust cam pulley to the crank pulley. On this side the belt is pulling the cam pulleys round. The other side, around the water pump and belt tensioner, essentially goes slack. On this side the belt is just feeding back up for the next turn. The tensioner just then takes up this slack. It has negligible effect on the drive side tension, and the side of the belt with the tensioner to be honest runs quite slack even when correctly tensioned; you're certainly not going to hear an audible note when you twang it. You might if you twanged the drive side, but the tension there is all driven by the cam springs etc. rather than belt tensioner. Link to comment Share on other sites More sharing options...
ECR Posted February 25, 2021 Author Share Posted February 25, 2021 Perhaps it's only effective on auxiliary belts? Link to comment Share on other sites More sharing options...
ECR Posted February 25, 2021 Author Share Posted February 25, 2021 I hear what you're saying Andrew....when the cam belt on a vx is installed and if you don't have the correct tensioning tool then Haynes advise that You should increase the tension so that you can just twist the belt through 90 degrees using just thumb and forefinger at the centre point of the longest run (that is from the exhaust cam to the crank pulley).applying tension makes the belt harder and harder to twist because tension is being applied to the belt. If the tension is increasing at this point then I'd guess that the frequency of the belt twang would also be increasing. This is also the point at which you check belt tension with my snap on timing belt tension setting tool.This should be the same regardless of engine type I would have thoughta bit of a head scratcher.... Link to comment Share on other sites More sharing options...
oilyhands Posted February 25, 2021 Share Posted February 25, 2021 I tried the app around 5 years ago when I first heard about it, I found it near impossible to get a clear 'twang' as free access to the belt is not easy in many of the K series installations I work on and also for the reasons Andrew explains above, this is especially true of the auto tensioner on the K series where the tensioner is spring loaded and it's authority cn be overcome quite easily.Oily Link to comment Share on other sites More sharing options...
rayjackson1950 Posted February 26, 2021 Share Posted February 26, 2021 I've always used the "turn belt 90deg" method on all my cars starting from a 1951 Mk ! Consul and it has never failed me. Link to comment Share on other sites More sharing options...
ECR Posted February 26, 2021 Author Share Posted February 26, 2021 Yes so did I till I felt the need for another tool....it worked fine for me also Link to comment Share on other sites More sharing options...
Paul Deslandes Posted March 1, 2021 Share Posted March 1, 2021 Hi RogerDo we know what range of frequencies we're talking about? Another way of measuring a resonant frequency is by absorption, where a signal source, acoustic on this case, is put close to the item of interest and the frequency swept. The belt will vibrate when stimulated at its resonant frequency. A bit like an opera singer shattering a wine glass. (I suspect a baritone might be required in this case).Probably impractical in reality but might be an amusing experiment.Paul Link to comment Share on other sites More sharing options...
ECR Posted March 1, 2021 Author Share Posted March 1, 2021 No idea of the frequency range Paul....... Link to comment Share on other sites More sharing options...
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